Device for the cooling of optoelectronic components and use of a flange joint used thereof

ABSTRACT

In a device for the cooling of optoelectronic components (1) with an evacuated cooler housing mounted on a base, in which there are provided at least one holding device for components (1) which is thermally coupled with the cold station of a cooling unit through at least one flexible metal band (19), the housing of the cooling unit is for vibrational decoupling connected with the cooler housing and sealed against atmospheric pressure through ring-shaped rubber-elastic sealing means. The at least one holding device (8), through a flexible metal band (19) thermally coupled to a cold station, of a refrigeration unit, that protrudes into the cooler housing, comprises a retaining plate (17) which is arranged on one end of a thin-walled, essentially prismatic or cylindrical body from a thermally poorly conductive material, specifically epoxy resin panels (9, 10, 11, 12). The end of the epoxy resin panels (9, 10, 11, 12) opposite the retaining plate (17) is rigidly mounted on the base of a cooler housing through a metallic base (13).

The invention concerns a device for the cooling of optoelectroniccomponents, specifically infrared diode lasers and infrared detectors,with an evacuated cooler housing which is mounted on a base in whichthere are provided a holding device for the components which through atleast one flexible metal band is thermally coupled with the cold stationof a cooling unit, and at least one window.

Such a device is known from the German patent document No. 34 45 674 andserves the cooling of infrared diode lasers and infrared detectors attemperatures down to the range of 10 K.

Such low temperatures are usually generated using two-stage coolersaccording to the Sterling principle with a continuous helium circuit,where the areas with low temperature are insulated from a housing atroom temperature by vacuum. The periodic helium expansion in the coolercauses mechanical vibrations which should only minimally transfer tothermally coupled diode lasers or detectors. The prior device providesfor that purpose a bar arrangement that features a bar which extendstransversely through the cooler housing and is mounted on both ends onrigid supports which are rigidly connected with a massive base on whichthe cooler housing is mounted with soft vibration dampers. While theknown design achieves an effective vibration decoupling of theoptoelectronic components, the cooler housing vibrates and thus also thewindow which is provided in the cooler housing for the emergent orincident radiation. Minute reflections on the window cause the backcoupling of fractions of the radiation intensity back to the radiationsupplies, which greatly influences especially diode lasers. With thewindow vibrating in the path of rays, the reflected radiation isirregularly modulated, causing severe disturbances in diode lasers.

Based on this prior art, the invention addresses the problem ofproviding a cooling device of the initially mentioned type where bothinterferences by vibration of the holding device and interferences byvibrations of the cooler housing are effectively suppressed.

This problem is inventionally solved in that the housing of the coolingunit is for vibrational decoupling connected with the cooler housing andsealed against atmospheric pressure through ring-shaped rubber-elasticsealing means and in that the singular holding device, thermally coupledthrough a flexible metal band with a cold station protruding into thecooler housing, features a holding plate which is arranged on one end ofa thin-walled, essentially prismatic or cylindrical hollow body fromthermally poorly conducting material, the other end of which body isrigidly connected with the base of the cooler housing.

An object of the invention is also the use of a flange joint featuringthe ring-shaped rubber-elastic sealing means.

In a suitable embodiment of the invention, the prismatic or cylindricalhollow body consists of four epoxy resin panels of slight materialthickness which rectangularly are connected rigidly with one another.Formed in this way is a rigid structure which in the panel directionnonetheless is a poor thermal conductor.

One arrangement offers the additional advantage that the temperature ofthe various optoelectronic components can be adjusted and controlledseparately. The distributor rails to which the copper bands of thevarious holding devices are thermally coupled are preferably so mountedthat they can thermally expand in longitudinal direction but, to avoidthe transmission of vibrations, cannot move as a whole.

The invention will be more fully explained hereafter with the aid of anembodiment illustrated in the drawing.

FIG. 1 shows a holding device of the device for the cooling ofoptoelectronic components in a perspective view;

FIG. 2, a sectional view of the cooler housing of the device;

FIG. 3, a lateral view of a distributor rail, partly in section,illustrating how the distributor rail is mounted on the base of thecooler housing;

FIG. 4, a plan view of the cooling device, partly in section;

FIG. 5, a modification of the embodiment according to FIG. 4 concerningthe rubber-elastic sealing means, with the flange joint drawn at alarger scale;

FIG. 6, an as yet uninstalled and, therefore, uncompressed sealing ring;

FIG. 7, another embodiment of the flange joint illustrated in FIG. 5 ata larger scale; and

FIG. 8, an as yet uninstalled axial ring seal for the flange jointaccording to FIG. 7.

FIG. 1 depicts in a perspective view an optoelectronic component 1which, e.g., may be an infrared diode laser or an infrared detector foroperation down into the 10-K range. Coordinated with the optoelectroniccomponent 1 is a diverging path of rays 2, which in FIG. 2 can be seenas a lateral view and with which there are coordinated a firststationary mirror 3 and a second stationary mirror 4 as well as a window5 in a cooler housing 6.

The cooler housing 6 is mounted on a base 7 illustrated in FIG. 2 andcontains in the embodiment illustrated in the drawing severaloptoelectronic components 1 with coordinated holding devices 8, thedesign of which can be seen best in FIG. 1.

The holding device 8 illustrated in FIG. 1, for the optoelectroniccomponent 1, is composed of four glass fiber-reinforced epoxy panels 9,10, 11 and 12 which with the aid of screws 14 are rectangularly screwedto a metallic base. The metallic base 13, in turn, is mounted on thebase 7, as can be seen from FIG. 2. Four bores 15 are provided in themetallic base for screw connection with the base 7.

The glass fiber-reinforced epoxy panels 9, 10, 11 and 12 have a lowspecific thermal conductance and a very small cross-sectional area. Theepoxy panel 9 is provided with conductor tracks 16 which, as will followfrom the subsequent description, are cooled the same as theoptoelectronic component 1 and, as compared to connecting lines, arebetter protected from damage.

The four epoxy panels 9, 10, 11, 12 screwed to the base 13 are on theirend opposite the base 13 screwed to a retaining plate 17, with the aidof screws 18. The retaining plate 17 consists of a thermally wellconducting metal and is thermally and mechanically connected with theoptoelectronic component 1. The heat generated by the optoelectroniccomponent 1 is removed with the aid of a first flexible copper band 19,in the fashion described hereinafter. The flexible copper band 19 isthermally well connected with the retaining plate 17 through a joiningpiece 20.

As illustrated by broken line in FIG. 1, the holding device 8 comprisesin its center area between the retaining plate 17 and the base 13 aprecooled metallic intermediate plate 21 which with the aid of screws 22is mounted on the four epoxy panels 9, 10, 11, 12 in order to increasein this way the rigidity of the cross sectionally rectangular prism orcylinder formed by the epoxy resin panels 9, 10, 11, 12. A precooling isaccomplished with the aid of the intermediate plate 21, by cooling itthrough a joining piece 23 and a second flexible copper band 24, as wellin the manner described farther down.

In FIG. 2 it can be seen how the first flexible copper band 19 isthermally coupled with a first distributor rail 25 and the secondflexible copper band 24 with a second distributor rail 26 which,somewhat below the first distributor rail 26 and parallel with it,extends within the cooler housing 6, which is sealed from the outsideatmosphere. The distributor rails 25, 26 consist both of a thermallywell conducting material and have a massive, approximately quadraticcross section. The mounting of the distributor rails 25, 26 on the base7 is identical.

FIG. 3 shows the mounting of the second distributor rail 26 on the base7. Arranged on the left end of the distributor rail 26 is a small ductor tube 27 of epoxy resin which on its bottom end features an inwardpointing flange 28 which, with the aid of the screw 29 which is threadedinto a threading provided in the base 7, is firmly secured to the topside 30 of the base 7 so as to produce a maximally rigid connection. Onthe end facing away from the base 7, the epoxy resin tube 27 possessesan outward pointing flange 31 which by means of several screws 32 isscrewed to the underside of the second distributor rail 26.

On the opposite end, the distributor rail 26 is mounted in a fashionpermitting it to be moved in the direction of double arrow 33 so as topermit length changes in case of temperature variations, but withoutpermitting other movement. On the end face which in FIG. 3 points to theright, the second distributor rail 26 is connected with a screw to aglass fiber epoxy resin platelet 34 which is bendable in the directionof double arrow 33 and extends in a plane which is perpendicular to thedrawing plane. A screw 35 is provided for mounting on the end face ofthe second distributor rail 26. The bottom end of the glass fiber epoxyresin platelet 34 is screwed to a shoulder 37 provided on the base 7,with a screw 36.

For cooling or heat removal, the second distributor rail 26 is thermallycoupled with a flexible metal band 38, for instance a copper band,through the use of a joining piece 39. The first distributor rail 25 iscorrespondingly connected with a flexible metal band 40.

As can be seen in FIG. 4 in plan view, the flexible metal band 38 isthermally coupled with the first stage 41 of the cold station 42 of adual-stage cooling unit 43 which produces vibrations. The second stage44 of the cold station 42 of the cooling unit 43 is connected with theflexible metal band 40, constituting a thermal coupling with theoptoelectronic component 1 through the flexible metal band 40, the firstdistributor rail 25 and the retaining plate 17.

The vibrating cooling unit 43 is mounted with vibration-damping rubberpads (not illustrated), which hardly transmit any vibration to base 7.As can be seen from FIG. 4, the cold station 42 of the cooling unit 43protrudes by way of a neck 45 provided on the cooling unit 43 and a neck46 provided on the cooler housing 6 into the interior of the coolerhousing 6. A connection and a seal between the cooling unit 43 and thecooler housing 6 is established with the aid of ring-shapedrubber-elastic sealing means in the form of a hose 47 which is slippedon the necks 45 and 46, is made from rubber, silicone rubber or flourcaoutchouc and is just stiff enough to absorb the atmospheric pressureload while on the other hand being sufficiently flexible to prevent atransmission of vibrations to the cooler housing 6. The hose 47 iscapable of performing both axial, angular and lateral as well astorsional movements.

As shown in FIG. 4, eight holding devices 8 as well as eight firststationary mirrors 3 and eight second stationary mirrors 4 are providedin the cooler housing 6. The device illustrated in FIG. 4 thus permitsthe operation and cooling of eight optoelectronic components 1, wherebythe temperature for each electronic component 1 can be adjusted andcontrolled separately. The desired temperatures of the individualoptoelectronic components 1 on the retaining plate 17 of the eightholding devices 8 are adjusted through electronically controlled heatingof the retaining plate 17.

Marked A1 as a whole, the flange joint according to FIG. 5 serves alsoto establish a vacuum-tight connection between the necks 45 and 46 thatis decoupled from vibration and movable toward all sides to a limitedextent, but serves also in a general way the connection between hollowbodies, which are illustrated enlarged in the section and may generallyconsist of tubes, sockets or housings with molded coupling ends. In thepresent case, the two hollow bodies are the coupling ends or necks ofthe cooling unit 43 and the cooler housing 6, with the illustratedflange joint A1 serving as a conduit for parts serving the electrical,mechanical and/or thermal connection, (for simplicity omitted in theenlarged section of FIG. 5 and FIG. 7).

The necks 45 and 46 will hereafter be called coupling ends. These aretubular and oppose each other at a spacing a₁. Near their respective endfaces K1 and K2, between which the axial spacing a₁ exists, both necks45 and 46 feature a circular groove, respectively N1 and N2, ofrectangular cross section, which is recessed in their peripheries.Inserted in the grooves N1 and N2 is a ring seal R1, R2 from elasticallydeformable sealing material, each having the form of a so-called O-ringor round-section ring. The ring seals R1, R2 sit in their grooves N1,R2, that is, on the cylindrical circular surface N3 of the groovebottom, with a slight prestress and have a ring thickness such that inthe as yet uncompressed condition (illustrated in the inserted,compressed condition) they protrude with a respective considerable partof their cross-sectional diameter D_(R) beyond the groove depth (compareFIG. 6). As the coupling sleeve T1 is now slipped over the two couplingends 45, each provided with a ring seal R1 and R2, or as the couplingends are slipped into the coupling sleeve T1, the two ring seals R1,R2--as illustrated--are flattened under elastic deformation, producing asealing surface pressure on the ring seat surfaces N3 of the groovebottom and on the as well cylindrical opposite seats N4 along the insidecircumference of the coupling sleeve T1.

When signifying the diameter respective surrounding circular seatsurfaces N3 of the coupling ends 45 and 46 as D_(KE) and the diameter ofthe surrounding opposite circular seat surfaces N4 of the circularsleeve T1 as D_(KH) and additionally the diameter of the as yetuncompressed ring seal R as D_(R), as separately drawn in FIG. 6 oncemore, the following relation is obtained: |(D_(KE) -D_(KH))|=k.D_(R)<D_(R), where the flattening factor k naturally must be smaller than 1.Factor k amounts to about 0.7 in the illustrated embodiment accordingFIG. 5. The "softer" the material of the ring seals the smaller may bek. The "harder" the material the greater will be k, the dimensionlessvalue of which may generally range between 0.5 and 0.9.

To achieve a limited mobility toward all sides, the flange joint A1according to FIG. 5 features gaps, and at that, the previously mentionedaxial gap a₁ between the end faces K1, K2 of the two coupling ends 45,46, and additionally radial gaps a₂ between the inside circumference ofthe coupling sleeve T1 and the outside circumference respective couplingends 45 and 46. To obtain an enlarged flexing gap, the coupling sleeveT1 is additionally beveled at T13 on those surrounding edges of its endfaces T11, T12 which are facing toward the coupling ends 45 and 46. Ascan be seen, the two coupling ends 45, 46, due to the flexing gaps andthe ring seals R1, R2 inserted between them and the coupling sleeve, canto a limited extent move relative to each other axially, radially andlaterally as well as tangentially. In the latter relative motion, thecommon axis b-b'-b" of the two coupling parts 45, 46, which normally arearranged equiaxially with one another, would break slightly at the pointb', i.e., the partial axis b-b' would be able to perform relative to thepartial axis b'-b" a slight break motion in the range of a few angulardegrees, without detriment to the vacuum tightness of the flange joint.This is true also for the other illustrated relative motions. The flangeconnection is characterized by a very good vacuum tightness because thegases which tend to penetrate from outside through the gap a₂ into theevacuated interior of the flange joint are confronted by a relativelysmall, rubber-elastic sealing cross section of the ring seals R1, R2,which additionally are compressed. The cross-sectionally rectangularcircular grooves N1, N2 serve to axially secure the ring seals R1, R2while enabling a relative motion for the coupling ends 45, 46 with theirinserted ring seals R1, R2 and the slipped-on coupling sleeve T1 inaxial radial, tangential, lateral and angular direction as alreadyillustrated, under retention of vacuum tightness. The coupling sleeve T1features on its inside circumference a collar T14 which trapezoidallytapers inwardly and whose two bevels t14 serve as an axial stop in bothaxial directions as regards the ring seals R1, R2.

In the third basic design of a flange joint A2 according to FIG. 7, aninner coupling sleeve T2 is in the fashion of a stopper or cork nestedover on both its ends--under insertion of at least one ring seal R1, R2each--by the two coupling ends 45, 46, in bottleneck fashion, which arelarger in diameter. The circular grooves N1, N2 corresponding to thecircular grooves N1, N2 of FIG. 5 are in the present example arranged onthe outside circumference of the coupling sleeve T2; their cross sectionis again rectangular. The inner ring seat surfaces are marked N5, theouter ones N6. The latter are arranged on the inside circumference ofthe two coupling parts 45, 46 in the thus, as also in FIG. 5, axialoverlapping area a₃ and are designed as stepped recesses, each with aslanted annular face n6 on its two ends facing away from each other,which serve as axial movement limitation for the coupling sleeve T2including the ring seals R1, R2.

The style A2 according to FIG. 7 enables an additional, elasticallydeformable ring seal R3 to sit on the outside circumference of the--nowinner--coupling sleeve T2 in the axial area between the two ring sealsR1, R2 or the corresponding radial ring seals, this additional ring sealR3--as illustrated--being flattened under elastic deformation, ininstalled condition, by the two end faces K1, K2 of the two couplingends 45, 46 facing each other to a value k'xD_(ax) of itscross-sectional diameter that exists in the as yet uncompressedcondition. Corresponding to FIG. 6, FIG. 8 depicts the cross section ofthe additional ring seal R3 in uncompressed condition, with a diameterD_(ax), and beside it there is illustrated the thickness of the ringseal R3 in installed, flattened condition with dimension lines, andmarked k'XD_(ax). The flattening factor k' in the axial direction isapproximately 0.75 in this example. Regarding its material-contingentsize, the same applies that was stated with regard to the flatteningfactor k.

In addition to the two end faces K1, K2 of the two coupling ends 45, 46,the inner beveled annular faces 50 of the two opposed, cross-sectionallytrapeziodal projections 51 serve as seating faces for the ring seal R3.The bevels in the end face area of the coupling sleeve T2 serving theenlargement of the flexing gap are marked t21. The advantage of thisflange joint A2 is specifically that it contains a two-step seal, thatis, the gases of the ambient space, for instance H₂ or He, mustnegotiate two seal barriers, namely the first one with the additionalring seal R3 and serially thereafter the second one with one of the tworing seals R1 or R2, so that this flange joint A2 is especially suitedfor the ultrahigh vacuum technology. The damped, vibrationally decoupledflange connection, which additionally permits a limited movement towardall sides, is retained with the flexural possibilities as illustratedalready with the aid of FIG. 5. The ring seals R1, R2, R3 consistpreferably of a material selected from the group suitable for ultrahighvacuum or high vacuum technology, for instance of an FKM fluor-elastomerviton, compound number 19457 or 19357. Another suitable, elasticallydeformable sealing material is Perbunan or Kalrez. Irrespective of thedesired degree of vacuum tightness, it may be suitable to glue the ringseals R1, R2, R3 on at least one of their annular seat surfaces N3, N4,K1, K2. Another suitable type of connection is vulcanizing, for whichpurpose the assembled flange joint is briefly heated, for instanceinductively, so that the contact surfaces of the ring seals enter withtheir seat surfaces respectively opposite seat surfaces locally into anintimate adhesive connection. However, this connection must not be of astrength such that the limited mobility of the flange joint will beimpeded.

Owing to their good properties regarding easy assembly and disassembly,vibrational decoupling, vacuum tightness and limited omnidirectionalmobility, the flange joints according to FIG. 5 through FIG. 8 havefavorable and versatile applications in the vacuum and high vacuumtechnology, as coupling element between pipes, sockets or housings.

We claim:
 1. An apparatus for the cooling of optoelectronic componentssuch as infrared diode lasers and infrared detectors said apparatuscomprising:a base; an evacuated cooler housing mounted on said base; acooling unit having a cooling unit housing and a cold station, saidcooling unit extending into said evacuated cooler housing; an elasticsealing means for sealingly coupling said cooling unit housing to saidevacuated cooler housing; at least one window in said evacuated coolerhousing; and a holding means within said evacuated cooler housing formounting the optoelectronic components, said holding means including aflexible metal band thermally coupled with said cold station, athin-walled hollow body composed of thermally poor conducting material,a retaining plate on one end of said hollow body, and a retaining baserigidly connected to said base.
 2. Device according to claim 1,characterized in that the thin-walled hollow body has a rectangularcross section and four sidewalls composed of glass fiber-reinforcedepoxy resin panels.
 3. Device according to claim 2, characterized inthat at least one of the epoxy resin panels includes electricalconnector tracks for electrical connection with the optoelectroniccomponents.
 4. Device according to claim 1 characterized in that theretaining plate is coupled with a second stage of the cold station ofthe cooling unit through a first flexible metal band, and in thatbetween the retaining plate and the base of the cooler housing there isarranged a metallic intermediate plate which is thermally coupled with afirst stage of the cold station of the cooling unit through a secondflexible metal band.
 5. Device according to claim 1 characterized inthat in the cooler housing there are provided a plurality of holdingmeans for optoelectronic components with coordinated windows.
 6. Deviceaccording to claim 5, characterized in that in the cooler housing thereare provided a plurality of holding means for optoelectronic componentswith coordinated mirrors.
 7. Device according to claim 5 characterizedin that the retaining plates connect through first flexible copper bandswith a common, thermally conducting first distributor rail which througha first flexible metal band is coupled with the second stage of the coldstation of the refrigeration unit, and in that the intermediate plateconnects through second flexible copper bands with a common, thermallyconducting second distributor rail which through a second flexible metalband is coupled with the first stage of the cold station of the coolingunit.
 8. Device according to claim 7, characterized in that the firstand/or second distributor rail is mounted on the base with the aid of arigid, thermally poorly conductive spacer and on its second end with theaid of a spacer which is deformable in the longitudinal direction of thedistributor bar.
 9. Device according to claim 8, characterized in thatthe rigid spacer is a glass fiber epoxy resin tube and the deformablespacer is a glass fiber epoxy resin plate which extends transverse tothe longitudinal direction of the distributor rail.
 10. Device accordingto claim 1 characterized in that the cooling unit housing is mountedwith vibration-damping rubber pads on the base which base extends beyondthe edge of the cooler housing.
 11. Device according to claim 1,characterized in that the elastic sealing means is connected torotationally symmetric, mutually spaced and opposed coupling ends of thecooling unit housing and the cooler housing, characterized in that thetwo coupling ends which are to be connected with each other and aremutually spaced and opposed and/or a coupling sleeve which overlaps withthe coupling ends while leaving a radial space in between includes ontheir circumference within the two overlapping areas couplingend/coupling sleeve at least one surrounding groove, said coupling endsurrounding grooves facing toward the coupling sleeve and said couplingsleeve surrounding grooves facing toward the coupling ends, saidsurrounding grooves forming annular seat faces at least one elasticallydeformable ring seal inserted in each said coupling end surroundinggrooves, each said seal being in the form of a round-sectionrespectively O-ring of a ring thickness such that the seal ringprotrudes from a surrounding groove in as yet uncompressed conditionwith a considerable part of its cross sectional diameter (D_(R))extending beyond the groove depth, and in that the nested arrangement ofthe coupling ends and coupling sleeve provided with the ring seals aredescribed by the equation:

    |(D.sub.KE -D.sub.KH)|=k x D.sub.R <D.sub.R,

where D_(KE) is the diameter of the surrounding annular seat surfaces ofthe coupling ends, D_(KH) is the diameter of the surrounding annularseat faces of the coupling sleeve and k is a dimensionless flatteningfactor, where k<1 and where the ring seals, is mounted condition, areflattened in the radial direction in their ring thickness to the valuekxD_(R) under elastic deformation, between their pertaining two annularseat faces.
 12. Device according to claim 11, characterized in that thecoupling sleeve is beveled on those surrounding edges of its end facesthat face toward the coupling ends, for creating an enlarged flexuralgap.
 13. Device according to claim 11 characterized in that an innercoupling sleeve is nexted in stopper fashion over on both itsends--under insertion of at least one ring seal each--in bottleneckfashion by the two coupling ends, which are larger in diameter than saidcoupling sleeve.
 14. Device according to claim 13, characterized in thatan additional, elastically deformable ring seal is disposed around theoutside circumference of the inner coupling sleeve in the axial areabetween that at least two radial ring seals, and in that this additionalring seal is flattened in installed condition under elastic deformationby the two end faces of the two coupling ends that face each other, to avalue k'xD_(AX) of its cross-sectional diameter (D_(AX)) that exists inas yet uncompressed condition, with the dimensionless flattening factorbeing k'<1.
 15. Device according to claim 13 characterized in that thering seals consist of a material selected from the group of elastomerssuited for the ultrahigh vacuum or high vacuum technology, for instancefrom an FKM fluor-elastomer viton of compound number 19457 or 19357,from Perbunan or Kalrez.
 16. Device according to claim 11 characterizedin that the ring seals are connected by gluing with at least one oftheir corresponding annular seat surfaces.
 17. Device according to claim11 characterized in that the ring seals are connected with at least oneof their corresponding annular seat surfaces by vulcanizing.